1. Field of the Invention
The present invention relates to the lubricating structure of a one-way clutch disposed in an automatic transmission.
2. Description of the Related Art
Conventionally, there has been a one-way clutch disposed in an automatic transmission.
The one-way clutch is comprised of an inner race, an outer race, and rollers arranged between the inner race and the outer race, for allowing relative rotation of the inner race and the outer race in only one direction.
The outer race and the inner race of the one-way clutch are connected to respective different rotational elements in the automatic transmission, or a rotational element and a transmission case, for controlling the rotational direction of each element.
When the outer race and inner race of the one-way clutch performs relative rotation, and the rollers are guided by the relatively rotating inner race to be forced toward cam peaks formed on an inner circumferential surface of the outer race, the rollers become caught in the form of wedges between the cam peaks of the outer race and the inner race to stop the relative rotation of the inner race and the outer race (hereinafter also referred to as “lock”).
On the other hand, when a rotary motion in the direction reverse to the direction in which the inner race and the outer race are locked is imparted to the inner race and the outer race, the rollers caught between the cam peaks of the outer race and the inner race are released to enable relative rotation of the inner race and the outer race.
The structure of such a one-way clutch is described in Japanese Laid-Open Patent Publication (Kokai) No. H02-278061.
The one-way clutch needs to supply lubricating oil to the rollers so as to prevent the rollers from being seized up.
In the case where lubricating oil is supplied from the inner race to the rollers, lubricating oil passages extending in the radial direction cannot be formed from the inner circumferential side of the inner race to the paths of the rollers since another rotational element is connected to the inner circumferential side of the inner race.
Therefore, according to Japanese Laid-Open Patent Publication (Kokai) No. H02-278061, as shown in FIGS. 7A and 7B, a lubricating oil passage 104 is formed from a side of the inner race 100 toward the trace of a roller 102 on an outer circumferential surface of the inner race 100 without passing through a spline tooth 101 which is formed on an inner circumferential surface of the inner race 100 so as to be engaged with a rotational element.
The lubricating oil passage 104 is configured such that particularly as shown in FIG. 7A, a direction 104a in which the lubricating oil passage 104 extends forms a predetermined angle γ′ with a perpendicular line 100b orthogonal to a rotational axis 100a of the inner race 100, and particularly as shown in FIG. 7B, a rotational axis 102a of the roller 102 and a direction 104a in which the lubricating oil passage 104 extends coincide with each other as viewed from the outer circumferential side of the inner race 100.
Because of the presence of the lubricating oil passage 104, a part between the lubricating oil passage 104 and the outer circumferential surface of the inner race 100 is a thin-walled part 105 having a smaller wall thickness as compared with other parts.
However, in the roller lubricating structure of the above described one-way clutch, there may be a case where as shown in FIG. 7B, an outer race, not shown, and the inner race 100 are locked in the state in which the roller 102 overlaps an opening of the lubricating oil passage 104 which is formed in the outer circumferential surface of the inner race 100.
In this case, if the inner race 100 is viewed from the direction of the outer circumference thereof, the rotational axis 102a of the roller 102 and the direction 104a in which the lubricating oil passage 104 extends coincide with each other, and hence a wide part of the roller 102 is supported by the thin-walled part 105.
Therefore, when the outer race and the inner race are locked, the thin-walled part 105 is deformed since the roller 102 is pressed against the inner race 100, and as a result, the durability of the one-way clutch is degraded.